The significantly increased use of organic hydrocarbon based polymeric compositions, such as polyolefins, in many and diverse applications or products, and the relatively high combustibility of such hydrocarbon based polymeric materials, and their propensity to spread or propagate burning due to flow and dripping at high temperatures, has greatly stimulated the investigation of flame-proofing measures for such organic polymeric compositions. Moreover, the high costs of fire damage in lives and property, and the current trend of the imposition of increasingly stringent safety requirements, have substantially intensified the pursuit of more effective and practical means of controlling or inhibiting combustion and its spread or propagation in many products and materials comprising organic polymers.
Notwithstanding prior developments of a great number of flame-proofing measures or additives resulting from this expanding effort, there remains a continuing need for improvements to meet current or new requirements in this area. The magnitude and urgency of this need for even greater improvements in this area and the proliferation of efforts and developments in this field are best evidenced by the ever increasing number of publications produced dealing with this subject.
Among the numerous developments which have concerned themselves with additives to polyolefin base compositions used and useful in wire coating are developments reported in the patents of Safford Pat. No. 2,888,419 and Safford et al Pat. No. 2,928,801. The Safford '419 patent is directed to an improvement in the extrudability of a filled polyethylene composition. The filler referred to in Safford '419 is a particulate filler and, particularly, "finely divided silicas, calcium silicates, aluminas, and carbon blacks", as pointed out in Safford '419 at the bottom of column 3.
The importance of the addition of silicone compound to the filled polyethylene is pointed out in Safford '419, column 1, where Safford states:
"However, in order to be extruded at high speeds the polymer should flow easily, form a smooth surface, and have a minimum of toughness or nerve. These properties are particularly difficult to obtain with filled polyethylene since filled polyethylene extrudes comparatively slowly and the extuded product has a rough surface."
Safford goes on to point out that a more extrudable composition is obtained by incorporating a minor amount of organopolysiloxane in the filled polyethylene.
Nowhere in the Safford '419 patent is there any mention of the prospect of obtaining benefit of addition of polysiloxane to unfilled polyolefin compositions nor is there any hint or suggestion of obtaining flame-retardant benefits from addition of organopolysiloxane additive or ingredient to either filled or unfilled polyolefin.
The Safford et al '801 patent concerns the addition of certain basic materials to a silica-filled polyethylene composition. The basic materials are recited at the top of column 2 of the patent and guanidine is identified as a preferred basic material. Also, other organic bases, basic organic salts and inorganic bases can be employed including lead oxide, magnesium oxide, zinc oxide, and a variety of other lead compounds. The basic materials are stated to have a "stabilizing effect" on uncured peroxide-containing filled polyethylene to permit their transportation in commerce without deleterious effects. Accordingly, the magnesium and zinc oxides are given as the equivalents of lead oxide and other lead compounds and guanidine is given as a preferred basic material.
As in the Safford '419 patent, there is no hint or suggestion in the Safford et al '810 patent of any benefit to be derived from use of the basic materials, including guanidine, lead oxide, magnesium oxide, zinc oxide or other lead compounds in relation to flame-retardance.